Alkyl isomerization of nuclearly alkylsubstituted hydrocarbons



ALKYL rsoM RIZAnoN F NUCLEARLY ALKYL- SUBSTITUTED HYDROCARBONS George Herve'rt, Downers- Grove, 11]., assignor to Uni-1 versal Oi! lroducts CompanyyDes Plaines, l]l., a corporation of Delaware N0 Drawing. Application Noyemb'er 2', 1956' f I Serial No.61 9f,953 I reclaims; (Cl. zen-66s This application is a contintiation-in-part of my copending application Serial No. 358,987, filed June 1, 1953, now abandoned. i

This invention relates to'. a process for converting tertiary alkyl-substituted aromatic hydrocar'bons to their corresponding secondary alkyl-substituted isomers. More specifically, the invention concerns an isomerization process for reacting a tertiary alkyl-substituted aromat1c hydrocarbon at isomerizing' conditions with an isomerizmg 2,830,103 Patented Apr; 8, 1958 ICC 'stituted aromatic hydrocarbon which comprises subjecting a tertiary alkyl-substituted aromatic hydrocarbon having at least five carbon atoms in the tertiary alkyl sub-.

stituent to the action of from about 0.1% to about by weight of a metal halide selected from the group consisting of the chlorides and bromides of aluminum and zirconium at a temperature of from about 0 to about 75 C. to thereby convert said tertiary alkyl substituent to a secondaryalkyl radical. V

A more specific embodiment of the invention 'conce'rns'a process for isomerizing a tertiary alkyl-substituted benzene hydrocarbon containing a tertiary alkyl grouphaving from 9 to about 18 carbon atoms to the ,corresponding alkyl benzene hydrocarbon in which the long chain alkyl group is a secondary. alkyl substituentwhich comprises contacting said long chain tort-alkyl benzene. hydrocarbon with from about 0.l% to about 25% by weight of aluminum chloride at a temperature of from about 20 to about 60 C. andthereafter recovering from the reaction mixture said secondary alkyl-substituted benzene hydrocarbon. In'the alkylation of aromatic hydrocarbons, particularly mono-nuclear aromatic hydrocarbons of the bencatalyst selected from a halide of aluminum or zirconium to thereby convert the tertiary alkyl substituent to a secondary alkyl group.

In certain processes" and in the production of various compositions for specific uses, it is essential in many instances that the organic charging stock to theprocsea or the compound employed in the composition'be an alkyl-substituted aromatic compound in which the alkyl group has a secondaryconfiguration; that is, .the alkyl group is attached to thoaror'natic nucleus through a secondary carbon atom (defined as a carbon atom to which two other carbon atoms ar'e' attached). Thus, in the case of the long chain alkyl-substituted aromatic hydrocarbon sulfonates, useful as detergents and surface active agents, the compounds in which the alkyl substitueht is attached to the aromatic nucleus through a secondary carbon atom are more elfective detergents (that is, the sulfonate has a greater cleansingaction or greater surface activity) and the resulting composition is generally less hygroscopic than sulfonatesofthcsarnc molecular weight and composition in which the alkyl group is attached to the aromatic nucleus through a tertiary or a primary carbon atom. The secondary alkyl-substituted aromatic hydrocarbons are also more resistant to side reactions which occur during the sulfonation'of an aromatic charging stock (that is, reactions such as dealkylation, tar formation, etc. which are foreign to the desired sulfonation reaction) consequently, more powerful and effective sulfonating agents, the use of which is accompanied by low consumption and Waste of reagents, may be employed in'sulfonating secondary al-' kyl-substituted hydrocarbons than for sulfonating the corresponding primary and tertiary is'oine'rs. Similarly, in the case of certain oxidation inhibitors which may be synthesized, from an alkyl aromatic hydrocarbon in a subsequent conversion reaction (as for example, in the production of certain alkyl-substituted p-phenylene diamine types of inhibitors) the isomers which contain a secondary alky'lsubstituent attached as one or more nitrogen atoms of tho amino sub's'tituent have greater inhibitor potency and are generally more soluble in' typical solvents than the corresponding tertiary and primary allryl-substi'tuted amines. Numerous other instances of preferred status or secondary alkyl aromatic hydrocarbons are knees in the chemical arts and such preference is sufficiently established to indicat'ethe utility of the present invention and its possible widespread application.

In one of its embodiments, the present invention relates to a process for producing a secondary alkyl stibzene series, with olefin polymers tofp'roduce an alkylate;

product having an alkyl group containing the same number of carbon atoms as the alkylating agent utilized in the process, it is known that certain acidic alkylation catalysts, such as sulfuric acid, hydrofluoric acid, the ferric halides, anhydrous hydrogen fluoride and boron trifluoride, are capable of catalyzing the alkylation reaction to produce a greater yield of alkylate product than certain other acidic alkylation catalysts of the metal halide type. However, the alkylates thus produced havea structure corresponding to tertiary alkyl-substituted aromatic hydrocarbons in which the alkyl group is bound to the aromatic nucleus through a tertiary carbon atom (that is, a carbon atom having three of its bondsattached to other carbon atoms). It has now been dis-' covered that the tertiary alkyl-substituted alkylates produced by the indicated alkylation catalyst may be conparticularly adapted to efiect the indicated isomerization.

Thus, it becomes possible to take advantage of the greater yield of alkylate product formed by an alkylation reaction catalyzed with the aforementioned acidic alkylation catalyst which produces tertiary alkyl-substituted aromatic hydrocarbons and by isomerizing the product with the presently specified isomerization cata lyst and at the particular reaction conditions suitable for the production of secondary alkyl-substituted aromatic hydrocarbons, the secondary alkylate may be produced with no substantial sacrifice in yield. By-employing the indicated combination of alkylation and isomeri'zation steps in a process in which the isomerization step follows the alkylation reaction, a yield of the secondary alkyl-substituted product may be obtained which corresponds with the yield of tertiary alkyl-substituted product, but the reduction in yield represented in the production of the secondary alkylate directly from the indicated isomerization catalyst in an alkylation reac-- tion is eliminated.

The isomerization reaction of the present processis directed to charging stocks characterized as tertiary alkylsubstituted aromatic hydrocarbons in which the alkyl group contains at least five carbon atoms. The reaction is applicable to aromatic compounds having not only mono-cyclic, but also polycyclic structures, including benassumebenzene, cumene, mono-, or di-butyl benzene and homo-' logues thereof. In the production of detergents, the benzene and toluene alkylates in which the alkyl substituent' contains at least nine carbon atoms, generally up to about eighteen carbon atoms per alkyl group, and being further characterized in having only one of such long chain alkyl substituents on the benzene nucleus, constitute one of the preferred charging stocks herein, since the'advantageous results realized in the application of the present process to such charging stocks are particularly evident in the improvement of the final product, as aforesaid. Thus, the alkylation products of benzene and toluene, formed by reacting the aromatic hydrocarbon with a long chain mono-olefin, such as a propylene tetramer fraction, utilizing concentrated sulfuric acid or substantially anhydrous hydrofluoric acid as a catalyst, is made up substantially-in its entirety of tertiary-alkyl-substituted isomers. When such tertiary alkylates are subjected directly to sulfonation to form the corresponding tertiary alkyl benzene or toluene sulfonates, the product is a detergent which, although a highly effective material for detergent use in aqueous solutions, nevertheless, is somewhat hygroscopic when exposed to atmosphere containing appreciable amounts of water vapor. If, however, the'tertiary alkyl-substituted alkylation product is subjected to an isomerization reaction of the character provided herein, the tertiary alkyl group is isomerized to a secondary alkyl group and if, thereafter, the resulting isomerized alkylate is converted to a detergent-type product by sulfonation, the resulting secondary alkyl aromatic sulfonate is not only a more effective detergent in that its surface activity is enhanced, but the product is substantially less hygroscopic and, therefore, resists caking when exposed to humid atmospheres than the corresponding sulfonate of the tertiary alkylate. The present isomerization process is, therefore, particularly applicable to benzene and toluene alkylates containing long chain alkyl groups which are substituted on the aromatic nucleus by virtue of a prior alkylation reaction efiected in the presence of an acid-acting catalyst which results in the substitution of a tertiary alkyl group on the aromatic nucleus.

The tertiary alkyl isomerization process of this invention is efiected catalvtically in the presence of a metal halide selected from the group consisting of the aluminum and zirconium chlorides and bromides, the catalyst being supplied to the isomerization reactor in a substantially anhydrous condition and preferably in the presence of the hydrogen halide corresponding to the metal halide utilized as catalyst in the reaction. The catalyst is supplied to the reaction zone in an amount corresponding to at least 0.1% and preferably from about to about 25% by weight of the tertiary alkyl aromatic hydrocarbon charged to the process, the amount of metal halide supplied to the reaction zone in any event being sufiicient to. convert the charge stock to the secondary alkyl-substituted aromatic hydrocarbon. The actual amount of catalyst required in any particular conversion depends upon such factors as the activity of the catalyst, the ease of isomerization, the stability of the aromatic reactant in the presence of the catalyst, and upon other factors mutually operable in the process. The catalyst is preferably introduced into the reaction mixture in a finely divided condition, accompanied by stirring of the reaction mixture to disperse the catalyst throughout the reaction zone or, alternatively, the catalyst may be dissolved in a suitable solvent therefor, prior to charging the same into the reaction zone. The hydrogen halide, if utilized during the conversion, is introduced into the reaction mix,

ture as the anhydrous gas below the surface Of 1 reastion mixture containing the catalyst. The reaction is desirably operated at a superatmospheric pressure, sufiicient to maintain the organic portion of the charge stock in substantially liquid phase condition, although pressures in excess of about 50 pounds per square inch are generally not required within the temperature range specified for thereaction, which may suitably be from about 0 to about 75 C. and preferably from about 20 to about 60 C., depending upon the ease of conversion andthe stability of the charge stock.

Aluminum and zirconium chlorides and bromides are unique among the various types of acid-acting catalysts, which includes, among others, such reagents as sulfuric acid, hydrogen fluoride, the zinc halides and ferric halides, etc., in that the chlorides and bromides of aluminum and zirconium effect isomerization of tertiary alkyl groups to their corresponding secondary alkyl isomers, Whereas 1 action zone of a suitable diluent of the reaction mixture during the' contact of'the selected metal halide with the alkylaromatic charge stock. Suitable diluents for this purpose which tend to reduce dealkylation of the aromatic compound, condensation thereof into tarry materials (particularly in the case of the phenols and long carbon utilized as diluent.

chain alkyl-substituted aromatic hydrocarbons) and other undesirable side reactions, include particularly the relatively inert, straight chain paraffinic or 'naphthenic hydrocarbons such as n-pentane, cyclohexane, n-hexane, n-heptane, etc. In certain cases, aromatic hydrocarbons,, such as benzene, toluene, naphthalene, etc., may be utilized as reaction diluents, as for example, when the reaction is effected at temperatures which result in the transfer of alkyl groups to the aromatic nucleus of the hydro- Particularly preferred diluents for the reaction are'the compounds which represent the charge stock free of isomerizable tertiary alkyl groups, such that any alkyl groups which split from the charge stock during the isomerization reaction are transferred directly to the diluent in the presence of the aluminum least equal in volume to the tertiary-alkyl-substituted aromatic compound subjected to isomerization, preferably in an amount of from about 0.5 to about 6 moles per mole of the latter charge stock.

Following the completion of the isomerization reaction, generally within a reaction period of from about 10 minutes to about 6 hours, the spent metal halide catalyst (aluminum or zirconium halide) which forms a sludge-like phase in the reaction mixture during the course of the isomerization may be recovered from the reaction mixture, either by separation of the sludge therefrom (for example, by decantation or by washing the reaction mixture with a stream of water which may contain a basic neutralizing agent, such as sodium hydroxide) or the product, unconverted charge stock and/or diluent may be distilled from the reaction mixture. Alternatively, the metal halide sludge may be separated from the reaction-mixture and utilized, at least in part, as the catalyst charge to a succeeding isomerization reaction. In the latter type of reaction, additional fresh metal halide is, preferably add edjo the sludg addiiidiial cliafie of alkyl for isomer'ization. Tlie i s dfil may Be separateu from the r therea'ction mixture by any su rior to c ample, by distillation. The separated solvent and EXAMPLE 1' p -Dodecyltoluen'e, whichb'y' ihfra re'd analysis was determined to be 98% by weightof the i'ertiary-dodecyl isomers, was prepared i n'a preliminary procedure by alkyla tion of toluene with dedecylene (the C 'ortetramer free- 6 formation of the secondary-liexylbenz'ene product from a' teftiary alkylatiiig agent.

EXAMPLE III A solution of 2 molar proportions of benzene and 1 molar proportion of p-di-(2,3 dimethyl-2-butyl)-berizene (a di -tertiary hexylbenzene) was added to a solution of 2 molar proportions of benzene which contained in solution by weight of the di-tertiary-hexylbenzene of anhydrous aluminum chloride,- tbe solution also being saturated with dry hydrogen chloride gas before mixing with the hexylbenzene-benzene solution It is thus evident that the resulting reaction mixture contains a totalmolar ratio of benzene to tertiary-'hexylbenzene of 4 to 1. The mixture was stirred for 4 hours at 30C., thereafter washed with water, dried, and fractionally distilled. A product yield of 52% of theoretical, 98% of 'which was mono-secondary-hexylbenzene, was recovered, none of the tion or a ropylene polymerization product) in the presenceo f 98.5% sulfuric acid catalyst and at a temperature of fibm about 30 to about 50 C., the alkylate product being separated from the resulting hydrocarbon layer formed, in the alkylation reaction by distillation of the 275 325 C. fraction therefrom; The tertiary do decyltoluene feed stock was charged into a stirred reaction vessel with various amounts of anhydrous aluminum chloride is'om eriza'tion catalyst, with and without added diluent (indicated in the following T'able I) and the reaction mixturethereafter heated atthe indicated ternperamre for 1.5 hours. The reaction mixture was thereafter washed witIi'Svolumes of water to' remove aluminum chloride and the recovered organic product dried and distilled to remove solvent (if any) therefrom. The following Table I indicates the results obtained by such conversion:

di-tertiary-hexylbenzene remaining unconverted.

In a similar experiment, utilizing the same charging stocks in the same molar proportions, except that anhydrous ferric chloride in an amount representing 20% by weight of the p di tertiary hexylbenzene was charged to the reaction in the form of a benzene solution there'- of, 95% of the product recovered (41% of theoretical based upon the hexylbenzene charged) was mono tertiary hexylbenzene and the product contained no detectable quantity of secondary-hexylbenzene.

The product formed by alkylating benzene with 1- chloro-3,S-dimethylbutane (an alkylating agent which produces a tertiary alkyl substituent) or with 1-ch1oro-, or 2-chloro-2,B-dimethylbutarie in the presence of anhydrous aluminum chloride and hydrogen chloride gas was consistently 2,Z-dirnethyl-3-phenbylbutane (a secondary-alkylbenzene) whereas the product formed by alkylating benzene with the above tertiary-alkyl alkylating agents in the presence of sulfuric acid, anhydrous hydrogen fluoride Table I ISOMERIZATION OF TEBTIARY-DODECELTOLUENE IN THE PRESENCE OF ALUMINUM CHLORIDE Char "e Stocks "gms:

pg'lertiary -Dodecyltoluene 100 100 262 100 Aluminum Chloride 10 2 26 10 Reaction Conditions:

Temperature, C 30 30 30 0 Contact time, Hrs 1. 5 1. 5 1. 5 1. 5 Product:

Loss to Catalyst Sludge, Wt.

Percent of Charge 11 0.2 8.7 1. 5 Loss to Dealkylation, Vol. Percent of Charge 34 10 27 15 Properties of 275-325 0. Product ND 1. 4909 1. 4900 1. 4923 1. 4909 Dispersion, 20 C- 118. 0 117. 7 118.1 118.0 Bromin? Noitnybfld It 1 0.1 0.2 0. 1 Ratioo sec. er 0 cc ouene in Product /60 10/90 40/60 40/60 65 is 1. 5 1. 5 V

*No'rn.Tertiary-dodeoyltoluene charging stock has a refractive index, N D, of 1.4907

a. dispersion, 20 C., of 116.8 and a bromine N o. of 1.0. 7

EXAMPLE II A solution of one molar proportion each of benzene and 2,3-dimethyi-2-phenylbutane (a tertiary-hexylbenzone) was introduced into a stirred alkylation reactor p and adjusted to a temperature of 30 C. To the resulting mixture, as the latter was stirred, was added 0.37 molar proportion (30% by weight of the tertiary--hexylbenzene) of anhydrous aluminum chloride dissolved in one molar proportion of benzene. The mixture was continuously stirred for 4 hours at the above temperature, fol lowed by washing the mixture with water to remove catalyst, drying the hydrocarbon product and subjecting the product to analysis. Infra-red analysis indicated that 100% of the product recovered (70% theoretical) was 2,2-dimethyl-3-phenylbutane (a secondary-hexylbenzene). It will be noted that alkylation and isomerization occur in a single one-step conversion reaction, resulting in the and ferric chloride was 2,3-dimethyl-Z-phenbylbutane, (a tertiary-alkyl benzene).

EXAMPLE IV temperature of 0 C., 75% of the dodecyltoluene product was the secondary isomer at a conversion temperature of 20 C., was the secondary isomer at 50 C. and

95-98% was the secondary isomer at 65 and 75 although a larger proportion of the charge stock is converted to side reaction products (i. e., alkyl benzenes and alkyl tolunes other than the dodecyltoluene charged) as the reaction temperature is increased. Above about 75 C., the conversion to side-reaction products becomes too excesssive to be considered a practical process.

In other experiments utilizing the same reactants except that zirconium chloride was substituted for aluminum chloride as catalyst, less conversion of the charge stock to side reaction products is obtained at the same temperatures at which aluminum chloride is employed, but the proportion of recovered alkylate converted to the secondary isomer is les s'than for, the aluminum chloride catalyzed reaction at the same temperature. .In general, higher reaction temperatures are required for the conversion of the same charge stock in the presence of zirconium halide catalysts than in the case of aluminum halide catalysts.

I claim as my invention:

1. A process for producing a secondary alkyl-substituted aromatic hydrocarbon which comprises subjecting a tertiary alkyl-substituted aromatic hydrocarbon having at least carbon atoms in the tertiary alkyl substituent to the action of from about 0.1% to about by weight of a metal halide selected from the group consisting of the chlorides and bromides of aluminum and zirconium at a temperature of from about 0 to about 75 C. tothereby convert said tertiary alkyl substituent to a secondary alkyl radical.

- 2. The process of claim 1 further characterized in that said aromatic hydrocarbon is monocyclic.

3. The process of claim 1 further charactcrized in that said aromatic hydrocarbon is a toluene hydrocarbon.

4. The process of claim 3 further characterized in that said tertiary alkyl substituent is in the para position.

, 5. The process of claim 1 further characterized in that said temperature is from about 20 to about 60 C.

6. The process of claim 1 further characterized in that the conversion of said tertiary alkyl-substituted aromatic hydrocarbon is effected in the presence of an inert diluent of the reaction mixture.

7. The process of claim 6 further characterized in that said diluent is benzene.

8. The process of claim 7 further characterized in that perature below the boiling point of said aromatic hydro-' carbon.

10. The process of claim 1 further characterized in that the reaction is effected in the presence of a hydrogen halide, the halogen of which corresponds to the halogen of said metal halide.

11. A process for isomerizing a tertiary alkyl-substituted benzene hydrocarbon containing a tertiary alkyl group having from 9 to about 18 carbon atoms to thereby fortn the corresponding alkylbenzene hydrocarbon in which said tertiary alkylgroup is converted to a secondary alkyl substituent which comprises contacting said tertiary alkyl benzene hydrocarbon with from about 0.1% to about 25 by weight of a metal halide selected from the group consisting of the chlorides and bromides of aluminum and zirconium at a temperature of from about 20 to about C. and thereafter recovering from the reaction mixture an alkyl-substituted benzene hydrocarbonin which the alkyl group contains from 9 to about 18 carbon atoms and wherein the alkyl substituent is attached to the benzene nucleus through a secondary carbon atom.

12. The process of claim 11 further characterized in References Citedin the file of this patent UNITED STATES PATENTS 1,972,599 Perkins et a1. Sept. 4, 1934 2,107,060 Olin Feb.,1, 1938 2,403,748 Olin July 9, 1946' 2,425,858 Beach Aug. 19, 1947 2,671,120 Ipatiefi Mar. 2, 1954 2,771,496 Hervert Nov. 20, 1956 

1. A PROCESS FOR PRODUCING A SECONDARY ALKYL-SUBSTITUTED AROMATIC HYDROCARBON WHICH COMPRISES SUBJECTING A TERTIARY ALKYL-SUBSTITUTED AROMATIC HYDROCARBON HAVING AT LEAST 5 CARBON ATOMS IN THE TERTIARY ALKYL SUBSTITUENT TO THE ACTION OF FROM ABOUT 0.1% TO ABOUT 25% BY WEIGHT OF A METAL HALIDE SELECTED FROM THE GROUP CONSISTING OF THE CHLORIDES AND BROMIDES OF ALUMINUM AND ZIRCONIUM AT A TEMPERATURE OF FROM ABOUT 0* TO ABOUT 75* C. TO THEREBY CONVERT SAID TERTIARY ALKYL SUBSTITUENT TO A SECONDARY ALKYL RADICAL. 